The invention relates to a method for controlling a hybrid automotive vehicle equipped with an internal combustion engine and an electric machine. The invention also concerns a hybrid automotive vehicle adapted to perform such a method.
Hybrid electric automotive vehicles, such as trucks, are equipped with energy storage systems which in many cases comprise one or several electrochemical batteries. The temperature of these batteries must be in a predefined operating interval to work properly. Batteries with too cold a temperature are not able to deliver enough electrical power, due to an increased internal resistance. In case a truck has to move alter being parked in a cold place for several hours, the vehicle may lack electrical energy, or more precisely may lack the ability to deliver enough electrical power at the beginning of the operating, period of the vehicle, which can affect the electric traction machine and/or electrically powered auxiliary equipments, such as lights or air conditioning system.
To avoid such issues, it is known to warm-up the battery prior to moving the vehicle, in order to permit the battery to deliver enough electrical current. Known battery warning techniques use auxiliary warming devices that induce a fuel over-consumption.
It is also known from JP-2004/245190 to perform, at the end of an operating period of a vehicle, a recharging step of the battery in order for it to be able to start the internal combustion engine at the beginning of the next operating period. This technique aims at making sure that the battery has enough energy to start the engine, taking into account the self discharge of the battery, but it does not guarantee that the battery has reached a temperature high enough to feed the electrical equipment of the vehicle with the right amount of electrical power when the engine is started again.
In a hybrid vehicle, if the batteries are not able to deliver enough electrical power supply to the electric traction machine, the internal combustion engine will be required to deliver a bigger proportion of the torque needed by the driveline to meet the requirement by the driver, which increases the fuel consumption. In addition, if available electrical power from the batteries is limited, it may affect other electrical consuming systems onboard the vehicle. Also, if the batteries are cold, it also affects the electrical power which they can absorb, for example during a regenerative braking of the vehicle. Due to this, the friction brakes of the vehicle will be required to dissipate more energy during a given braking phase, energy which will not be recovered and will result in further increased fuel consumption.
The invention aims, according to an aspect thereof at proposing a new method for controlling a hybrid automotive vehicle which promotes heating up the energy storage system of the vehicle without using auxiliary warming devices, or at least significantly reducing the need for such devices, thus allowing to provide as soon as possible an optimum level of available electrical power to the vehicle.
To this end, an aspect of the invention concerns a method for controlling a hybrid automotive vehicle, equipped with an internal combustion engine and an electric machine connected to an energy storage system, each of said internal combustion engine and said electric machine being adapted to deliver torque to a driveline of the vehicle. This method is characterized in that it comprises at least the following steps:
a) during a mission of the vehicle, estimation of the temperature of the energy storage system at the beginning of the next mission of the vehicle,
b) if the temperature estimated at step a) is below a threshold value, recharging, before the end of the current mission of the vehicle, the energy storage system on the basis of the temperature estimated made at step a);
c) if the energy storage system has been recharged at step b), then, at the beginning of the next operating period of the vehicle, heavily discharging the energy storage system.
Thanks to aspects of the invention, a cold temperature, which may prevent the battery from property functioning at a later stage, is forecast and a certain amount of electrical energy is stored in the battery before the end of the mission of the vehicle. This amount of electrical energy is used at the beginning of the next mission of the vehicle to heat the energy storage system by Joule effect obtained by a heavy discharge of the battery, using the self heating of the battery due to its increased internal resistance at lower temperatures. This allows the battery to more quickly reach a temperature at which it can exchange more electrical power with the vehicle's electrical systems, especially with the electrical machine 4.
According to further aspects of the invention which are advantageous but not compulsory, such a method may incorporate one or several of the following features:                If the temperature estimated at step a) is below the threshold value then the energy storage system is recharged at step b) with a state of charge higher than a normal operating state of charge target used when the temperature estimated at step a) is above the threshold value.        At step c), the energy storage system is discharged by reducing the ratio between the torque delivered to the driveline by the internal combustion engine and the torque delivered to the driveline by the electric machine.        The method comprises after step c), further steps of:        
d) measuring or estimating the temperature of the energy storage system.
e) if the temperature measured or estimated at step d) is superior to a threshold temperature value, adjusting a state of charge level target of the energy storage system to a normal value.                At step b), recharging of the energy storage system is performed by progressively increasing a state of charge SOC target of the energy storage system.        At step b), the ratio between the torque delivered to the driveline by the internal combustion engine and the torque delivered to the driveline by the electrical machine is increased, and whereas a given amount of the torque delivered by the internal combustion engine is converted by the electrical machine into electrical energy and stored in the energy storage system.        At step a), the estimation is made on the basis of weather forecast data.        At step a), the estimation is made on the basis of weather statistic data.        The method comprises, prior to step b), a further step of:        
f) determination if the mission of the vehicle is about to end.                At step f), determination is made by geographically locating the vehicle with respect to a predefined trip.        At step f), determination is made by comparing the distance covered by the vehicle during the current mission to an average amount of distance covered during previous missions of the vehicle.        At step f), determination is made by a device triggered by the driver of the vehicle. This invention also concerns a hybrid automotive vehicle equipped with an internal combustion engine and an electric machine connected to an energy storage system, each of said internal combustion engine and said electric machine being adapted to deliver torque to a driveline of the vehicle. This vehicle is characterized in that it comprises means to estimate, during a mission of the vehicle, the temperature of the energy storage system at the beginning of a next mission of the vehicle, means to charge, before the end of the current mission of the vehicle and if the temperature estimation is below a threshold value, the energy storage system on the basis of the temperature estimation, and means to heavily discharge the energy storage system at the beginning of the next mission of the vehicle.        
According to further aspects of the invention which are advantageous but not compulsory, such a vehicle may incorporate one or several of the following features:                The vehicle comprises an electronic control unit adapted to control a state of charge target of the energy storage system.        The electronic control unit is adapted to control the ratio between the torque delivered to the driveline by the internal combustion engine and the torque delivered to the driveline by the electric machine.        The vehicle comprises a temperature sensor adapted to measure the temperature of the energy storage system.        The vehicle comprises means to determine if the mission of the vehicle is about to end.        